Mark Gordon wasn’t a believer in the paranormal when he purchased the 150-year-old building he transformed into one of Whitehall’s most popular late-night hot spots, but nearly four years later he’s not sure what to think.

Gordon said he and the staff of Big G’s Pub have heard and seen things in the building he simply can’t explain.

He’s heard children playing on the second floor, even though it’s unoccupied, he’s smelled perfume and cigar smoke even thought he was alone in the building, and he and his staff have seen doors swing open on their own.

“One the second floor there is a long hallway, and I swear that you can hear kids running back and forth laughing. It kind of makes the hair on the back of your neck stand up,” Gordon said with a chuckle from inside the pub on Monday evening.

His cook once saw a man peering over a set of bat-wing doors that separate the kitchen from the bar even though she had believed she was alone. And just a few weeks ago, Gordon said he heard loud clapping that he couldn’t attribute to anyone in the building.

And Gordon isn’t the first to witness the phenomena.

He said his friend Billy Jones lived in the building as a child about 40 years ago and “saw some things that were unbelievable.”

Unable to explain the sights, smells and noises, Gordon contacted Albany Paranormal Research Society, a nonprofit group that investigates the paranormal in the Capital region and surrounding areas and its members agreed to conduct an investigation.

Debbie Stockwell, co-founder and director of the organization, said the group doesn’t search for evidence of the paranormal, but instead tries to find evidence that uncovers the veil of what seems unexplainable.

“We try to find normal reasons to explain why these things happen,” she said. “For instance, if there is mold in the building it can cause hallucinations. There are a lot of different factors that contribute to this. We try to do everything scientifically.”

She said the group uses high tech equipment to record noises and electromagnetic fields. They also rely on historical information about the building, like who owned the property in the past and what the building was used for.

And the building, which is located at 66 Main St., has a very long and interesting history.

Gordon said the four-story building, which he painstakingly renovated in 2008, dates back to at least the 1860s.

The third floors used to be a stage and performing area where many concerts and plays were performed in the 1930s, and the second story, which most recently housed several apartments, was at one time the offices of local dentist Dr. Arthur Yellen.

And then there are the stories that Gordon and Stockwell can neither confirm nor deny, like a rumor that a woman once perished in a fire in the building many years ago.

On Sunday the group came and investigated the phenomena.

“They were here from 7 p.m. to midnight and had digital recording devices and cameras,” Gordon said. “Something happened but they wouldn’t tell me much”

He said the group is going to analyze its findings and send him a report in three months.

“I don’t know what to expect,” Gordon said. “I was never a believer, but I’m starting to change my mind a little.”